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Galinsoga (aka, Peruvian daisy or shaggy soldier) flowerheads are small (1/4" across) with 4-8 (usually five) widely separated 2.5 mm long, white ray florets with three teeth at their tips. The 15-35 disc florets are yellow. Both ray and disc florets are fertile; the ray florets are pistillate while the disc florets are perfect (both pistils and stamens). The fruit (a cypsela) consists of a black, conical seed suspended beneath about five off-white, papery, fringed scales that act as a parachute. A poisonous plant (Tridax procumbens) with nearly identical flowers (but distinctly different leaves) is (luckily) restricted to FL and TX in the U.S. so not likely to show up in Jackson Park. The name Galinsoga ciliata, sometimes still used for Galinsoga quadriradiata, is invalid (ITIS); according to the USDA Plants database, C. ciliata has been superceded by either G. quadriradiata or G. urticifolia.

Galinsoga

Galinsoga quadriradiata

galinsoga [Blooms: Jun-Oct]

Cream gentian the leaves are olive-green, lance-shaped with a pronounced fold along the midvein, 3" long and 2" across, and clasp the stem. Although most leaves are opposite (in pairs), the leaves just below the flowers occur in a whorl of three. The flowers are mostly apical, some version of white or cream, tubular, with the petal's veins outlined in green, about 1-2" tall and 3/4" across, and oriented near-vertically. The five petals remain tightly appressed, with only a small opening where their apices meet; the five stamens and pistil with a bifurcated stigma are usually hidden from view. Bumblebees are the primary pollinators.

Gentiana

Gentiana alba

cream gentian [Blooms: Jul-Oct]

Carolina crane's-bill flowers are small (about 1/4-3/8" across), in small clusters on stubby pedicels. Each flower contains five dull-green, very hairy, lance-shaped sepals with long, scarlet-tipped awns on the tips, five white to pinkish-lavendar petals shorter than the sepals, ten stamens with tan anthers, and five stamens fused at their bases. The fruit is spherical with a very long beak divided longitudinally into five sections; when ripe (the fruit turns bright red) , the beak splits violently into five strips attached to each other at their distal ends, flinging the seeds far from the parent plant. Carolina crane's-bill has white to pinkish flowers with sepals longer than the petals; cut-leaved crane's-bill (Geranium dissectum) has deep pink to purple flowers with sepals the same length as the petals.

Geranium

Geranium carolinianum

Carolina crane's-bill [Blooms: May-Jun]

Cut-leaved crane's-bill's very attractive flowers occur in pairs. The base of the flower is covered by five green sepals the same length as the petals, covered externally in glandular hairs; the tips of the sepals are drawn out into a short (1-2 mm) awn that is scarlet-tipped. The five petals are a deep pink to purple in color; there are five pink stamens with purplish-yellow anthers; the five styles produce a deep pink, star-shaped stigma at their tips. The fruit consists of five hairy spheres around the base of an elongate "crane's bill" which splits explosively when ripe into five strips attached at their distal ends, flinging the seeds far and wide. Carolina crane's-bill (Geranium carolinianum) has white to pinkish flowers with sepals longer than the petals; cut-leaved crane's-bill has deep pink to purple flowers with sepals the same length as the petals.

Geranium

Geranium dissectum

cut-leaved crane's-bill [Blooms: May-Jun]

Wild geranium flowers are about 1.5 " across; they have five spindle-shaped, green sepals with a short red-tipped awn at their tips and five purplish-pink petals, twice the length of the sepals, that are egg-shaped with broady rounded tips and have darker fine radiating lines that function as necter guides. The ten stamens have pale yellow anthers; the single pistel has five carpels that splay at the tip of the pistil into a starfish shape. The anthers produce pollen while the five styles' stigmas remain pressed together; after the anthers are spent, the stigmas separate. The fruit is a candle-shaped, cylindrical structure with a sharp tip. The carpels build up tension as they dry until they spontaneously snap near their base (above the sepals); as the carpel violently curls upward, it flings a single seed considerable distances like a tiny catapult.

Geranium

Geranium maculatum

wild geranium [Blooms: Apr-Jun]

Ground ivy flowers are 1/2" long and arise from the leaf axils; they are purplish, trumpet shaped, with a notched upper and lower (the largest) lobe and two small side lobes; the "throat" of the lower lobe is hairy. There are four stamens (two long, two short) with purple to blue anthers, and a single pistil with a bifurcated purple style. The corolla of the flowers is cupped by a hairy, green, tubular calyx that has 15 ridges distributed around the calyx running longitudinally, and five triangular teeth at the apex of the calyx. The fruit is a nutlet that nestles in the calyx.

Glechoma

Glechoma hederacea

ground ivy [Blooms: Apr-May]

Woodland sunflower flower stalks tend to be hairier than the stem. The flowerheads are 1.5-3" across with 8-15 ray florets with yellow petals (with a tiny notch at the tip) and over 40 yellow, tubular disc florets with five spreading apical lobes. Flower bracts cup the back of the flowerhead in four series, light green, pointed, hairy along their margins, and typically recurved. Only the disc florets are fertile; the ray florets are sterile. Woodland sunflowers can be recognized by their nearly-sessile or sessile, opposite, leaves and broad leaf bases.

Helianthus

Helianthus divaricatus

woodland sunflower [Blooms: Jul-Oct]

Sawtooth sunflower flowerheads are 2.5-4" across with 10-20 bright yellow ray florets and over 100 tubular golden-yellow disc florets with five protruding brown anthers fused around a yellow style with a bifurcated stigma. Behind the flowers are multiple layers of spreading bracts that are pointed with hairy margins, especially near their base. Only the disc florets are fertile; the ray florets are sterile. (This is true throughout the genus Helianthus, although this situation seems more understandable (to me) than the the situation in the genus Silphium, where the opposite is true.) Sawtooth sunflowers can be distinguished from other Helianthus spp. by their hairless, reddish-purple stems; the arching leaves with a longitudinal fold are also characteristic but not definitive.

Helianthus

Helianthus grosseserratus

sawtooth sunflower [Blooms: Jul-Sep]

Downy sunflower is a very attractive sunflower which blooms in late summer. The composite flowers arise directly from the main stem. Each flowerhead is 2-4" across with 15-30 yellow ray florets and over 75 yellow disc florets in a 1" diameter central disk. Individual ray florets are sterile, the "petal" is about 1-1.5" long. Disc florets are about 1/4" long with five triangular lobes at the end of a tubular corolla; five stamens with white filaments (fused around the base of the style) and purple-brown anthers; and a single style, bifurcated at its tip, which protrudes above the stamens.

Helianthus

Helianthus mollis

downy sunflower [Blooms: Aug-Sep]

Western sunflower is a spindly plant that leads a double life. It is a perennial that first produces a very large (1.5' across) basal rosette of leaves; that basal rosette in turn produces a 2-4' tall, nearly leafless, stem. Clusters (a panicle) of 1-4+ flowerheads are present on pedicels less than 6" long emerging from the stem or upper leaf axils. The flowerheads are 1.5-2.5" across, with 8-20 ray florets, each bearing oblong yellow petals, and over 50 tubular, yellow disc florets with five lobes on their tips and five protruding brown anthers fused around a yellow style with a bifurcated stigma. Only the disc florets are fertile; the ray florets are sterile. (True throughout the genus Helianthus, although that seems more understandable (to me) than the situation in the genus Silphium, where the opposite is true.) Behind the flowerhead are 20-25 lance-shaped bracts (phyllaries) 5-7 mm long with pointed, green or straw-colored tips; there are often hairs round the margins of the phyllaries. The long, sparsely-leaved stem is diagnostic.

Helianthus

Helianthus occidentalis

western sunflower [Blooms: Aug-Sep]

Jerusalem artichoke should rightly be called a "sunflower" like the other four members of the genus Helianthus present in Jackson Park. Five to fifteen flowerheads ride on hairy peduncles up to 8" long and are 2.5-3.5" across; each is cupped by 2-3 overlapping series of phyllaries (bracts) that are more triangular than lance-shaped, hairy, and sharply pointed. The flowerheads consist of 10-20 sterile, yellow ray florets; the 60+ fertile disc florets consist of tubular yellow corollas about 1/4" long with five lobes at their apex and five protruding brown or black anthers fused around a yellow style with a bifurcated stigma. Jerusalem artichoke was cultivated by the indigenous peoples of the midwest for its tasty and carbohydrate-rich tubers.

Helianthus

Helianthus tuberosus

Jerusalem artichoke [Blooms: Aug – Oct]

Ox-eye sunflower (aka, false sunflower) flowerheads are 1.5-3.5" across with a prominant, gumdrop-shaped central disk; the plane of the flowerhead is horizontal, not vertical like most other (true) sunflowers. The 1.5-3" wide flowerheads consist of 10-18 yellow, tubular ray florets with yellow to golden-yellow, elongate-oval petals with notched tips and with two longitudinal folds in each petal; the numerous (10 to over 75) disc florets are yellow, tubular with five (brighter) yellow spreading apical lobes on the tubular corolla. Both disk florets and ray florets have a protruding, bifurcated style; the disc florets also have five stamens with brownish anthers which encircle the style below the paired stigmas. Behind the flower are two series of hairy bracts, the outer layer longer than the inner (a diagnostic character) and a velvety pedicel 1-8" long. Ox-eye sunflower is a "false sunflower" because both the ray and disc florets are fertile and can produce seeds; in true sunflowers, only the disc florets produce seed. The posture of the flower (horizontal rather than nodding towards the vertical) is also distinctive.

Heliopsis

Heliopsis helianthoides

ox-eye sunflower [Blooms: May-Jul]

American hops male and female flowers occur on separate plants. Actual female (pistillate) flowers occur in tight clusters ("aments") 3/4" long of 10-50 flower pairs on a stalk that arises from a leaf axil, each pair subtended by a bract; each flower has two long, thin styles. Male flowers have five pale green spreading sepals and five short, banana-shaped stamens. The fruit is a cone-like structure of overlapping bracts (originally present at the base of the female flowers) that surround the seeds; it is (obviously) found only on the female plants.

Humulus

Humulus lupulus

American hops [Blooms: Jul-Sep]

Wild hydrangea canes produce a flat terminal panicle 3-6" across with 100-500 flowers of two kinds — small, fertile flowers filling most of the area and a few, sterile pseudo-flowers around the margin that are 3-4 times larger than the flowers in the center and seem to function only as an advertisement for pollinators. The central, fertile flowers are about 1/4" across with a green calyx made of five separate sepals; five greenish-white or cream petals about 1/8" long; 8-10 stamens with long filaments and oblong, white anthers; and a pistil bearing two styles with knob- or club-like stigmas. The sterile, outer pseudo-flowers have 3-4 fused petal-like, white bracts (or sepals; sources differ) with a central structures that visually is reminiscent of stamens or styles; the pseudo-flowers persist long after the inner flowers have been fertilized and have produced a two compartment seed pod that is ribbed and bears a pair of tiny horns (the styles) on its upper end. Wild hydrangea is relatively rare in northern Illinois; in Jackson Park it prefers wooded area by walking paths.

Hydrangea

Hydrangea arborescens

wild hydrangea [Blooms: Jun-Aug]

Panicled hydrangea (Hydrangea paniculata) is an exotic perennial native to China and Japan that may grow as either a shrub or a tree. Neither Natureserve Explorer nor the USDA Plants database acknowledge the presence of panicled hydrangea in Illinois, but the Morton Arboretum and the University of Illinois Extension both explicitly do. Panicled hydrangea is widely sold in nurseries; commercial cultivars reach 10-15 feet high and wide. It definitely occurs in Jackson Park, near our native species — wild hydrangea (Hydrangea arborescens) — but I have not seen it in direct competition with wild hydrangea. The inflorescence is a conical panicle typically covered with two types of flowers — large, nominally-sterile flowers and smaller, bisexual flowers — scattered across the surface of the panicle. The "sterile" flowers are white or greenish white with typically 4-5 (3 in Jackson Park) elliptical to round lobes (actually sepals) 1/2-1" long and 1/3-2/3" across (8-15 mm). In Jackson Park, at least half the nominally sterile flowers bear a small, budlike structure in their center that exhibits three lobes (petals?), have 3-6 distinct stamens with small anthers, and a two-lobed central structure that is probably a reduced pistil. It is not clear whether either the pistils or stamens are functional. The bisexual flowers usually have five tiny (less than 1 mm long and wide) sepals, five petals 3-4 mm long and 0.1-0.3 mm wide (which often fall off the flower), 2-5 mm long stamens, and an ovary with 2-4 spreading styles (two in Jackson Park specimens) that are 2-3.5 mm long and are fused at their bases. After fertilization, the petals and stamens wither and fall off; the remainder of the flower forms an oblong, 3-5 mm long, seed capsule. The easiest ways to tell panicled hydrangea (H. paniculata) from wild hydrangea (H. arborescens) is: (1) the inflorescence is conical or pyramid-shaped in panicled hydrangea but a flat disc or shallow dome in wild hydrangea, and (2) the showy, "sterile" flowers in panicled hydrangea are scattered evenly across the surface of the inflorescence in panicled hydrangea, but are restricted to the margins of the inflorescence of wild hydrangea (rather like the inflorescence of the much more common but unrelated American cranberry, Viburnum opulus var. americanum). Wild hydrangea is much more common than panicled hydrangea in Jackson Park.

Hydrangea

Hydrangea paniculata

panicled hydrangea [Blooms: Jul]

Giant St. John's wort stems and branches terminate in clusters (cymes) of 1-5 flowers 2-2.5" across; the central bud opens first. Giant St. John's wort has the largest flower of all the St. John's worts found in Illinois. Each flower has five green sepals 1/3 the length of the petals; five bright yellow, often twisted, petals; more than 100 yellow stamens with yellow anthers; and a yellow-green pistil with five distinct styles fused at their bases, each with red stigmas at their tip. Five carpels are present in the flask-shaped ovary. The fruit is a five-chambered, bullet-shaped structure up to 1.25" long and 1/2" wide, initially green, turning brownish-black with maturity; the capsule is topped with the remnants of the (five) styles and contains numerous lozenge-shaped, 1 mm long, black seeds. (When fully mature and with appropriate magnification, the seeds look like ears of corn.) Note in particular the very large (2") flowers and the five styles on the pistil of giant St. John's wort — most other Hypericum spp. have either one or three styles. Kalm's St. John's wort also has five styles, but that is a much smaller and woody plant with narrower leaves and much smaller flowers.

Hypericum

Hypericum ascyron

giant St. John's wort [Blooms: Jun-Aug]

Kalm's St. John's wort is a 1-3 ' tall shrub, largely restricted to the Great Lakes basin of the U.S. and Canada; it is formally listed as "critically endangered" in Illinois (but is quite common in Jackson Park). The flowers occur in clusters (corymbs) of 3-7. Individual flowers are 1-1.25" across; they have five light green, lance-shaped sepals half the length of the petals, five spreading golden-yellow petals, 150-200 stamens with yellow anthers, and a five-lobed yellow ovary with five (partially or completely fused) styles. The ovary often is markedly five-lobed. The fruit is a teardrop-shaped capsule resting on the five widely-spread sepals containing five (occasionally four) carpels; the capsules are initially green, then turn bright red, then finally brown as the numerous black, oblong seeds mature. Woody lower branches and the strongly five-lobed pistil and fruit are distinguishing characters that separate this species from other Jackson Park St. John's worts.

Hypericum

Hypericum kalmianum

Kalm's St. John's wort [Blooms: Jun-Aug]

Common St. John's wort flowers are ~3/4" across, with five green sepals, five oblong yellow petals, three widely-spreading styles (and three carpels) with scarlet stigmas on top of a globular yellow ovary, and numerous (45-85) stamens with yellow anthers. The filaments of the stamens fuse into three groups near their bases. Unique among the St. John's worts in Illinois, common St. John's wort has petals with tiny black dots (glands full of essential oils) that are restricted to the petal margins. (Hypericum punctatum, spotted St. John's Wort, also has black dots on the petals but, in that species, they extend to the interior of the petals.) These black glands may also occur sparsely on the anthers. The fruit is a three-chambered, bullet-shaped structure 1/4" long, initially green, turning reddish-brown with maturity; the capsule is topped with the remnants of the (3) styles and contains numerous seeds. Common St. John's wort contains chemicals that may interact adversely with a number of common pharmaceuticals despite its widespread use in traditional medicine and may be toxic to livestock in large doses.

Hypericum

Hypericum perforatum

common St. John's wort [Blooms: Jun-Aug]